Generally, an Electronic Control Unit (ECU) of an Electrical Power Steering (EPS) system controls the steering of a vehicle by detecting steering torque according to the manipulation of a steering wheel of a driver through a torque sensor.
For the torque sensor of the EPS system, a battery voltage inputted into the ECU is regulated in a regulator of the ECU and then used as a driving power of the torque sensor.
However, there is a drawback in the conventional torque sensor in that if the battery voltage is lower than a predetermined value due to an instantaneous overload of the vehicle or the like, the voltage outputted through the regulator of the ECU to the torque sensor turns into a low voltage, smaller than a tolerance of a rated voltage. This causes a decrease of the output of the torque sensor and the like by an abnormality of the torque sensor and results in an inaccurate steering of the vehicle.
There is another drawback in that if a phase variation occurs due to a temperature variation in the coil part of the torque sensor or the like, a distortion phenomenon of a torque detecting signal is generated by a lack of a precise sampling of the signal, thereby deteriorating the accuracy of the torque detecting signal.